This application is based on and claims the benefit of priority of the prior French Patent Application No. 9716193 filed on Dec. 19, 1997, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a method for the control of an electronic circuit of the type comprising at least one access pin to receive and/or deliver control signals as well as a control unit for the implementation of said method.
2. Discussion of the Related Art
It is known that the devising, designing and manufacture of a circuit of this kind is very costly. First of all, the circuit has to be defined from a functional viewpoint. Then it has to be simulated by means of computer-assisted design software. Then, it is necessary to prepare the pattern of the masks needed to make the circuit physically on an integrated circuit substrate of silicon. Finally, it still has to be tested once it has been integrated into a plastic package.
This is why the manufacturers of integrated circuits often make new products out of prior products by adapting them so as to modify only what is strictly necessary.
There are also known ways of making applications specific integrated circuits (ASICs) by assembling a plurality of functional blocks taken out of a collection of drawings of elementary circuits (a xe2x80x9clibrary of drawingsxe2x80x9d in the language of those skilled in the art). The advantage lies in the fact that the drawing of the functional blocks is designed and validated in advance. Similarly, the test vectors to be used to verify the efficient operation of the circuit are known and can be used again to test the integrated circuit block by block. Only new test vectors must be created to check that the assembly works efficiently. All this helps reduce development time and, therefore, the cost of a new integrated circuit.
However, it may happen that an existing integrated circuit or a functional block available in a library of drawings, while it corresponds functionally to the specifications of a new circuit to be designed, cannot be used again in an identical form within the framework of a new application. This may be the case for example when the earlier circuit is a logic circuit that is controlled by or delivers electrical signals whose levels of voltage are incompatible with those of the application envisaged. The earlier circuit may also be one that communicates with the exterior according to a specific protocol which cannot be implemented in the new application envisaged. Those skilled in the art will then be required to substantially modify the earlier circuit or the available functional block which, in practice, takes up almost as much time and is almost as expensive as developing a completely new circuit. Now these costs may weigh very heavily in the cost of manufacture of a new integrated circuit especially if the quantities to be produced are too small to enable these costs to be recouped in the long term.
Accordingly, an object of the invention is the re-utilization, without modification, of the design of an electronic circuit of the type in applications where the integrated circuit cannot be controlled by means of n sources of control signals (n being strictly greater than one) but, on the contrary, through a single means for the serial transfer of data.
In accordance with an aspect of the invention, a method and device for the control of a circuit having at least one control I/O comprises the generation, in a control unit, of said control signals from data received serially through a means for the serial transfer of data. To this end, the method of controlling according to the invention comprises the following steps:
a) extraction of a control word included in the data received serially;
b) decoding of the control word extracted in the previous step in order to perform an operation, as a function of the value of the control word for modifying the logic state of at least one control signal.